Most man utilities can write postscript instead of directly to terminal. You can use that to achieve exactly what you want. Though this is not exactly in the terminal itself.
Example: I don't have zsh for comparison but on my OS X machine, running `man -t bash | open -f -a Preview` results in this: https://dl.dropboxusercontent.com/u/845567/bash%281%29.pdf
Here's zsh: https://drive.google.com/file/d/0B_jWp8d11aB5Wi15eVdJS1Nhdk0...
It kinda sucks that you can't just pipe directly to Preview, but I suppose we should be grateful this wonderful pipeline does actually work!
Yes, you can choose a default font. You need to change your /etc/man.conf, find the line that starts with TROFF, and add new options. For example, to use Palatino as the default font, you should additionally provide the option `-f P`. Then you'll get this output: https://dl.dropboxusercontent.com/u/845567/bash%281%29%20Pal...
And there's an interesting history to that split: https://en.wikipedia.org/wiki/Times_New_Roman#Linotype_relea...